The technical field of this invention is phototherapy and, in particular, methods and devices which employ optical fibers and flexible light waveguides to deliver radiation to a targeted site, such as the heart.
Cardiac rhythm irregularity, i.e., fibrillation, is a pathological condition of heart muscle that can be present in one or more of the atria or the ventricles of the plant. Until recently, efforts to alleviate these irregularities have focused on pharmacological treatments. While pharmacological treatments can be effective, drug therapy requires regular administration of so-called xe2x80x9cbeta-blockerxe2x80x9d type drugs or prompt intervention with a therapeutic inhibitor of fibrillation. Moreover, drug therapy is frequently accompanied by side effects such as dizziness, nausea, vision problems or other difficulties.
Abnormal arrhythmias can occur in the atrium or ventricle, and are referred to, respectively, as at rial fibrillation and ventricular fibrillation. Atrial fibrillation is an atrial arrhythmia characterized by rapid randomized contractions of the atrial myocardium, causing an irregular, often rapid heart rate. Three of the most common types of atrial arrhythmia are ectopic atrial tachycardia, atrial fibrillation and atrial flutter. Atrial fibrillation can result in significant patient discomfort and even death due to an irregular heart rate. Ventricular fibrillation is an arrhythmia characterized by fibrillary contractions of the ventricular muscle due to rapid repetitive excitation of the myocardial fibers without coordinated contraction of the ventricles. Loss of synchronous atrioventricular contractions compromises cardiac hemodynamics and can lead to varying levels of congestive heart failure, or stasis of blood flow, which increases the likelihood of thromboembolism. It is difficult to isolate a specific pathological cause for atrial fibrillation although it is believed that the principle mechanism is one or more of the electrical reentry circuits within the left and/or right atrium. Such reentry circuits interfere with the normal rhythm of electrical signals that course the heart muscle to contact in a synchronized manner in order to perform its normal pumping function.
Recently, it has been suggested that arrhythmias can be treated by ablation procedures performed within the heart and/or the coronary blood vessels. Ablation of predetermined locations within the heart to form linear tracks or scars through the walls (transmural) of the heart or blood vessels can provide a natural barrier to the formation of reentry circuits. These linear scars must be well defined within the heart to be effective. For example, the ablation catheters used to perform the ablation procedures produce scar tissue at the selected site from one of a number of different energy sources employing direct current, laser, microwave, or ultrasound energy. However, many of these energy sources are limited by the requirement that physical contact with the tissue to be treated must be maintained during the procedure. Moreover, the present ablation systems do not provide a suitable way to know when sufficient energy has been applied to the tissue, without unnecessary scarring of exposed tissue, or to what extent the energy has penetrated the tissue.
Another serious complication of presently known ablation techniques can occur when such procedures are performed within a vein or artery. Veins and arterial blood vessels are delicate physiological structures. Traumatic stressing of a vein or artery, such as by surgery, or thermal destruction of tissue, can lead to stenosis, a reduction or collapse of the inner diameter of the blood vessel causing a reduction in blood flow. For example, many of the current techniques used to treat fibrillation are directed to ablation of tissue within the pulmonary vein, thus leading to stenosis of the site treated. Unfortunately, the resultant stenosed vessels reduces the blood flow back to the heart, thereby causing discomfort, pulmonary hypertension and other serious side effects. Often times, the patient must undergo additional procedures to treat the stenosis, which in turn causes a new site to be traumatically stressed and ultimately stenosed. This repetitive cycle can have serious consequences for the patient.
A need therefore exists which circumvents the above-described deficiencies of currently available ablation techniques for the treatment of cardiac fibrillation.
Methods and apparatus for phototherapy are disclosed in which laser light or other radiation is projected in an annular pattern without requiring direct contact of the energy source, e.g. a laser (via fiber), with the targeted tissue. The invention is particularly useful in cardiac therapy in creating annular conduction blocks in atrial chamber issue, e.g. centered about but at a defined distance from a pulmonary vein orifice or coronary sinus orifice, to eliminate aberrant wave conduction.
The invention is particularly useful for inducing phototherapeutic processes in tissue, including ablation and/or coagulation of the tissue. Typically the optical apparatus is contained within a catheter including a flexible elongate member having a proximal end, a distal end and at least one longitudinal lumen extending therebetween. The distal end of the flexible elongate member can be open or includes a transparent cap, a centering balloon, or a centering coil. The optical apparatus of the invention can be fixed or a distal location or preferably disposed within the first lumen in a manner that permits axial motion within the lumen. The optical apparatus serves to project light through, or from, the distal end of the flexible member. The optical apparatus can include an optical fiber and other light projecting elements.
The optical apparatus of the invention can include an optical fiber and a beam-shaping waveguide for projecting an annular pattern of light. Radiation, e.g., infrared, visible or ultraviolet light is propagated through the optical fiber that is optically coupled to a lens or other optical waveguide. The lens is configured to project an annular light pattern such that an annular lesion is formed in tissue. In one embodiment, the annular light pattern expands over distance like a hollow cone to project a beam in the form of a ring or a halo. The waveguide can include a graded intensity lens (GRIN) or other known refractive or reflective optics to project the annular light pattern.
The apparatus of the invention can also include a balloon member fixedly attached to the catheter. Injection of a solution or gas expands the balloon, thereby forcing blood and/or other body fluids from the tissue site.
In certain embodiments, the optical apparatus of the invention is slidably positioned within the lumen of a catheter proximate to a tissue site. Positioning the optical apparatus at the particular location within the balloon and/or by adjusting the size or shape of the balloon permits control over the size and distance of the forwardly projected annular ring. This control permits the annular beam of projected light to be dynamically changed to specifically target the atrial tissue surrounding the pulmonary veins or coronary sinus.
The present invention also pertains to methods for forming an annular lesion in a tissue by phototherapeutic processes in tissue, including ablation and/or coagulation of the tissue. The methods include introduction of an optical apparatus proximate to a tissue site via, for example, a catheter. The optical apparatus includes a pattern-forming optical waveguide that is in communication with a light transmitting optical fiber. Energy is transmitted through the optical fiber, such that radiation propagated through the optical fiber and waveguide projects an annular light pattern, e.g., a circle or a halo. By these methods, an annular lesion can be formed in a targeted tissue. In certain embodiments, the tissue forms a lumen, e.g., vascular, atrial, ventricular, arterial, venous, brachial, or urethral lumen. Preferably the methods include projecting an annular light pattern via an optical apparatus that is located at a defined distance from the target tissue.
The present invention further pertains to methods for forming annular lesions in cardiac tissue, e.g., trabecular tissue, by phototherapeutic processes that can include ablation and/or coagulation of the tissue. The methods include positioning an optical apparatus at a location proximate to the cardiac tissue via, for example, a catheter. The optical apparatus includes a pattern-forming optical waveguide optically coupled to a light transmitting optical fiber. Energy is transmitted through the optical fiber, such that radiation is propagated through the optical fiber, the waveguide and GRIN lens to forwardly project an annular light pattern, e.g., a circle or a halo. In a preferred embodiment, a balloon is inflated against the tissue, thereby forcing blood and/or body fluids away from the tissue targeted for treatment. Light energy is then passed through the optical apparatus onto the targeted tissue such that an annular beam is projected onto the site, thereby causing ablation, coagulation or photochemical processes to occur.
The present invention also pertains to methods for treating or preventing atrial arrhythmias by phototherapeutic processes in atrial tissue. These processes can include ablation and/or coagulation of the tissue. The methods include introducing an optical apparatus proximate to atrial tissue via, for example, a catheter. The optical apparatus includes an optical waveguide in communication with a light transmitting optical fiber. Energy is transmitted through the optical fiber, such that radiation is propagated through the optical fiber and the waveguide projects an annular light pattern. The annular light pattern forms an annular lesion in the atrial tissue, thereby treating or preventing atrial arrhythmias.
In another aspect, the present invention is directed to methods of treating atrial arrhythmia. The methods include introducing a photoablation instrument into an atrium, positioning the photoablation instrument at a location within the atrium where light from an optical assembly can be projected onto an inner surface of the atrium, and exposing a region of atrial tissue surrounding a pulmonary vein to radiation from an optical assembly without substantial ablation of the vein itself. The photoablation instrument includes an optical assembly for projecting a beam of radiation, e.g., an annular beam of radiation. The optical assembly can include an optical fiber and a GRIN lens and/or other refractive or reflective elements.
In certain embodiments, the resultant annular lesion has a mean diameter of between about 10 mm and 23 mm, preferably, greater than 10 mm, more preferably greater than 15 mm, and in some instances preferably greater than 20 mm or even greater than about 23 mm. Generally, the annular lesion has a width (of the annular ring) of less than 5 mm, preferably about 3 mm, and in some applications preferably less than or equal to 1.5 mm. Preferably, the treatment occurs without ablation of into the pulmonary vein tissue. For example, the center of a pulmonary vein at its mouth in an atrial chamber can be defined with an anchorage element as described below. A annular beam of radiation can be projected to form a ring like lesion concentric with the pulmonary vein center, but at a radial distance of at least 5 mm, preferably greater than 7 mm from the vein""s centerline.
According to another aspect of invention, a region of atrial tissue surrounding the targeted pulmonary vein is exposed to infrared radiation from the optical assembly at a wavelength ranging from about 805 nm to about 1060 nm, more preferably from about 900 nm to about 1000 nm and most preferably from about 940 nm to about 980 nm. More generally, the energy and wavelength of the radiation are chosen to penetrate substantially the entire thickness of the atrial wall, e.g., between about 1 to about 4 mm, preferably, between about 2 to about 3 mm in depth.
In one embodiment of the present invention, the photoablation instrument includes an expandable balloon element adapted to surround the optical assembly upon inflation. The balloon element can be inflated with deuterium oxide or deuterated water, such that the inflated balloon provides a low loss transmission pathway for radiation between the optical assembly and an inner surface of the atrium. A region of atrial tissue surrounding a pulmonary vein can then be exposed to radiation from the optical assembly. Deuterium oxide provides the advantage that it absorbs less energy from the transmitted energy, thereby preventing the balloon from becoming heated.
In still another aspect, the present invention provides a phototherapeutic apparatus that includes a light transmitting optical fiber, a graded index lens and a conical reflector. Radiation propagated through the optical fiber when connected to the graded index lens is partially reflected by the conical reflector, to project an annular pattern of phototherapeutic radiation. In a preferred embodiment, a high refractive index material, such as silicone, is in communication with the optical fiber and graded index lens and the graded index lens and conical reflector. Typically, the optical fiber and graded index lens are located between about 0 mm and about 2 mm of each other and the graded index lens and the conical reflector are located between about 0 mm and about 0.5 mm of each other. A preferred graded index lens has a length of 1.66 mm and a diameter of 1 mm.
The methods of the invention can be performed therapeutically or prophylactically. In one embodiment, the treatment method is performed on the atrial wall around the atrial/pulmonary vein juncture or around the pulmonary vein or coronary sinus, e.g., not inside the atrial or pulmonary vein but about the pulmonary or atrial surface. A circular or ring-like section outside the pulmonary vein is created by the method of the invention. Formation of one or more circular lesions about the outside diameter of a vein, impedes the conduction of irregular electrical waves in the atrium.